The present invention relates to a method and an apparatus for measuring width of a selvage rubber portion extending in transversal direction of a coating sheet wherein a plurality of cords arranged in parallel and in substantially the equal interval are integrally coated with rubber and the like so that the cord portions are expanded, from the most externally positioned cord portion of said coating sheet.
The coating sheet wherein the cord portions are expanded includes, for example, rubber coating sheets embedding reinforcing cords, which are used for production of a tire and the like. This coating sheet is produced by coating a tire cord fabric in which a plurality of cords 1-1, 1-2, . . . , 1-n are arranged in parallel and in substantially the equal interval as shown in FIG. 1 with rubber 3 by feeding the fabric into a calender having rolls 2-1, 2-2, 2-3 and 2-4 as shown in FIG. 2 in the longitudinal direction shown by an arrow A. FIG. 3 shows a cross-sectional view of the thus produced coating sheet 4 and the coated portions (cord portions) 5-1, 5-2, . . . , 5-n where the cords 1-1, 1-2, . . . , 1-n are coated with rubber, are expanded, that is the thickness (diameter) of the coated portions (cord portions) is larger than that of the flat portions 6 connecting the cords. The coating sheet has selvage rubber portions 7 which extend outwardly from the most externally positioned cord portions 5-1 and 5-n respectively in an uneven width. This coating sheet 4 is cut in the given angle and width and the thus cut coating sheets are press-bonded and connected at the selvage rubber portions 7 so that the cord makes the given angle to the longitudinal direction to obtain a long cord inclined fabric. In the thus formed cord inclined fabric, it is a necessary requirement for producing the tires which are high in the drive feeling, and are strong and safe, that the distance between the cords is constant. For the purpose, it is necessary to precisely measure the width of the selvage rubber portions 7 to be press-bonded and connected, and to cut the portions at the given width.
As such methods for measuring the selvage rubber portion, it has been proposed that the position of the most externally positioned cord is detected prior to coating the cords with rubber and the position of the most external end of the coating sheet after rubber coating, that is the end surface of the selvage rubber portion is detected, whereby the width of the selvage rubber portion is measured. When the cord is steel, the position of the most externally positioned cord of the coating sheet after rubber coating is detected by an eddy sensor and the like and concurrently the position of the end surface of the selvage rubber portion is detected by the other detecting means to determine the width of the selvage rubber portion. But, in the former measuring method, there is a defect that before or after the rubber coating, if the position of the most externally positioned cord is varied during rubber coating in order to detect the position of the most externally positioned cord and the end surface of the selvage rubber portion, it is impossible to precisely measure the width of the selvage rubber portion. In the latter measuring method, the positions of the most externally positioned cord and the end surface of the selvage rubber portion are concurrently detected after rubber coating to determine the width of the selvage rubber portion, so that the width of the selvage rubber portion can be always precisely measured. However, when the cord comprises organic fibers, such as nylon and the like, this method is not applicable, so that this method cannot be ordinarily used.